The Determination Of Trans Fatty Acids In Vegetable Oil And The Change Regulation In The Heating Process

Trans fatty acids(abbr. TFAs), known as "the time bomb" on the table, are unsaturated fatty acids containing at least one trans double bond. Trans fatty acids mainly derive from ruminant animal fat and muscle fat, grease hydrogenation processing, vegetable oil high temperature and long time heat-treating. Studies show that eating too much food containing trans fatty acids may accelerate atherosclerosis, lead to cardiovascular disease and diabetes mellitus. Many international organizations and countries have taken relevant measures to reduce or limit the content of trans fatty acids in food. China is a big consumer of fried food. Smoked fish, deep-fried dough sticks, fried chicken, French fries and so on, are very impressive in people's daily life. Therefore the deep study on trans fatty acids in edible oil is increasingly urgent and the first and most important thing is to establish an effective detection method.At present, gas chromatography, which characteristic is high sensitivity, low detection limit and high accuracy, is mostly used to detecte trans fatty acids. First, proper extraction agent is used to release the trans fatty acid triglyceride in edible oil into free fatty acids. Then methyl esterification is taken place and the products are detected by GC. Two important tasks in the determination of trans fatty acids by GC are to establish high efficient pretreatment process including extraction and methyl esterification and to optimize GC separation condition. In this paper, studies were made on the high resolution GC method for the determination of trans fatty acids. First, influence factors in pretreatment process including the types of extraction solvents and esterification agents, extraction and esterification time and esterification temperature, so on, were chosen by orthogonal design experiment method. Then the chromatographic conditions were optimized used 8 TFAs and 37 FAMEs as standards. This established GC detection method could measure 8 common kinds of trans fatty acids in edible oil and its linear correlation, detection limit and recovery rate could meet the requirement of qualitative and quantitative. Even so, the separation of unsaturated fatty acid isomers and the detailed chromatographic separation of fatty acid need further optimizing.In this paper, study was also made on the content and species of trans fatty acids in commercially available edible blend oils with the heating temperature increasing from 80 ? to 240 ? and heating time prolonging from 1 h to 4 h. Results showed that the kinds and content of the trans fatty acids in experimental oils all increased when the heating temperature reached 240 ? and the latter was even 2 times as much,as original.